Many punch assemblies in commercial use such as the punch assembly described in U.S. Pat. No. 4,989,484 while otherwise very good require time-consuming disassembly using hand tools in order to remove the punch to sharpen the punch tip followed by reinstallation and readjustment of the length of the punch. This operation is labor intensive and, of course, lengthens the downtime of the equipment. Reduced press productivity is problematic particularly with respect to punch assemblies used in high-speed automated punch presses and punch assemblies that have a stripper for assisting in the removal of the workpiece from the punch tip. These punch assemblies require almost complete disassembly so that the punch can be removed for sharpening followed by reinstallation of the punch into the punch assembly using hand tools. While manual length adjustment mechanisms have been previously developed as described, for example, in U.S. Pat. Nos. 4,375,774; 5,329,835; 5,647,256; 5,839,341; 5,884,546; 6,755,110; 6,782,787; and 7,168,356, the patented mechanisms are not adapted for upgrading existing punch assemblies of the general type described in U.S. Pat. No. 4,989,484 as well as for original equipment because of the way the punch assembly is constructed. The present invention is directed to providing a solution to this problem as well as other shortcomings of the prior art. All references cited herein shall be considered to be disclosed as fully and completely as though reproduced herein in their entirety.
In view of these and other deficiencies of the prior art, it is a general object to provide manual, i.e. tool-free, length adjustment for a punch assembly which allows the adjustment to be made without disassembly.
A more specific object of the invention is to find a way to enable a punch assembly of the kind described in U.S. Pat. No. 4,989,484 to be upgraded by the owner so that it can be manually adjusted without tools or disassembly.
Another object is to provide a manually adjustable punch that is constructed so as to reliably prevent misalignment or uneven wear that could otherwise occur between various punch assembly components.
Another object of the invention is to enable the punch to be removed manually from the punch housing without tools.
Another object is to provide for positive drawbolt retention so as to prevent the drawbolt from accidentally falling out during disassembly.
Yet another object is to provide for tooless adjustment at both ends of the punch assembly, namely, manual punch length adjustment at the top end and manual stripper release at the lower end of the punch assembly.
These and other more detailed and specific objects of the present invention will be better understood by reference to the following Figures and detailed description which illustrate by way of example but a few of the various forms of the invention within the scope of the appended claims. Directions, e.g. “upwardly” and “downwardly,” are relative so as to better describe the Figures and are not intended to limit spatial orientation of the invention as a whole.